Over the Wire [0] is also great if you're curious about this sort of thing. The webapp challenges became one of my initial exposures to SQL -- as well as to injections as a concept -- and later became the basis for a whole rabbit hole on Web scraping that I haven't fully gotten out of haha
The CLI ones are also how I learned (among other things) to run single commands over ssh, which I ended up needing to kill stuck browser processes on my dev box at a previous job. Hilariously, I ran across this (as well as a reason to use it) a week after a boss of mine told me it wasn't an effective use of my off time
There's a tip-of-my-tongue one I keep hoping would crop up again here, but I haven't been able to find since: it was something about a site that showed example exploits inspired by high-profile breaches that happened IRL. It's unfortunate, bc that sounded fascinating